1. Field
Example embodiments of the present invention relate generally to wireless communication systems including relay nodes.
2. Description of the Related Art
While cellular networks are ubiquitous, users continue to experience inconsistent and unpredictable performance in mobile applications. While performance degradation may be a result of network congestion or an obstructed path of a wireless signal, in any cellular deployment performance may degrade towards the edge of a cell due to interference from, for example, neighboring cells. Data transfer rates at the edge of the cell (cell edge rates) are typically the worst transfer rates for the cell.
Some wireless networks include relay nodes (RN) which work in conjunction with base stations (BS), for example extended node Bs (enB), to extend the coverage of the BSs and improve cell edge rates. One type of RN is the type II RN defined by 3GPP documents for LTE-Advanced technology.
A simple example of downlink operation of a type II relay, integrated into a hybrid automatic repeat request (HARQ) operation is described as follows. An eNB sends a transport block to a UE and RN. The RN may successfully decode the transport block, while the UE fails to decode the transport block. The RN retransmits the transport block at some later time, possibly simultaneously with eNB, and the UE receives the transport block correctly because the channel quality on the RN-UE link is significantly better than on the eNB-UE link. Accordingly, the manner in which RNs are used in wireless networks to supplement the wireless coverage of BSs can improve the quality of service experienced by UEs in a wireless network.
Defining a method or architecture for operating relay-aided cellular networks is a difficult problem and signaling schemes are not known even for a simple case of a single source, relay and destination. Furthermore, only upper bounds on the capacity region are available even for this simple case.
Current solutions for improving cellular network throughput and edge rates in cellular networks using relays include independently scheduling users and relays, and/or increasing the density of served users on a one time frequency slot. One method of increasing the density of served users includes adding infrastructure in so-called cell-splitting schemes (e.g., micro or pico cells).